1 Technical Field
The present invention relates to rotating electric machines which have welds formed by welding end portions of electric conductors for forming a coil and weld-insulating members that cover, at least, the surfaces of the welds, and to methods of manufacturing the rotating electric machines.
2 Description of Related Art
There are known rotating electric machines which have welds formed by welding end portions of electric conductors for forming a coil and weld-insulating members that cover, at least, the surfaces of the welds.
In the rotating electric machines, there is generally a large temperature difference between when the rotating electric machines are in an operating state and when the rotating electric machines are in a stopped state. Therefore, with the temperature change in the rotating electric machines, the welds and the weld-insulating members repeatedly undergo expansion and contraction. However, the material composition of the welds is different from the material composition of the weld-insulating members; thus, the coefficient of thermal expansion of the welds is also different from the coefficient of thermal expansion of the weld-insulating members. Consequently, due to the repeated expansion and contraction of the welds and the weld-insulating members with the temperature change, the adhesion force of the weld-insulating members to the respective welds is lowered, thereby making it easy for the weld-insulating members to peel off from the respective welds.
Japanese Patent No. JP5510709B2 discloses a rotating electric machine which has joints (or welds) formed by welding end portions of electric conductors for forming a coil and electrically-insulative resin members (or weld-insulating members) that cover the surfaces of the joints. The electric conductors are made of a copper oxide having a high oxygen concentration. During the welding of the end portions of the electric conductors, blow holes are created to form uneven portions on the surfaces of the joints. The resin members are provided to cover the surfaces of the joints which include the uneven portions. Consequently, compared to the case of having no uneven portions formed on the surfaces of the joints, the adhesion areas of the resin members to the respective joints are increased. Moreover, during the formation of the resin members, the molten resin members are impregnated into recesses of the uneven portions of the joints and solidified therein into a wedge shape. As a result, it is possible to suppress the adhesion force of the resin members to the respective joints from being lowered due to the repeated expansion and contraction of the joints and the resin members with the temperature change in the rotating electric machine; thus, it is possible to suppress the resin members from peeling off from the respective joints.
However, in the rotating electric machine disclosed in the above patent document, the uneven portions of the joints are formed by the blow holes that are randomly created in the surfaces of the joints. Therefore, on the surfaces of the joints, there are randomly-sized protrusions formed into a dot-shape. Consequently, stress may concentrate on peripheral portions of the resin members which abut some of the protrusions. As a result, the adhesion force of the peripheral portions of the resin members to the respective joints may be lowered, causing the resin members to peel off from the respective joints.